The present invention relates generally to an automotive suspension assembly and more particularly to an improved apparatus and method of adjusting wheel camber in an automotive vehicle.
The ride and handling characteristics of an automobile often center on the interface between the vehicle and the road. This interface, the vehicle tires contact with the road, manages the input of forces and disturbances from the road, and is the final link in the driver's chain of output commands. Tire characteristics, linkage mechanisms, and vehicle geometry are therefore key factors in the effect the road has on the vehicle, and in the effectiveness of the output forces that control vehicle stability and cornering characteristics. Design and adjustment of these elements allows for improved control and performance of the vehicle.
One such design element is known as camber. Camber is the lateral inclination of the wheel. If the wheel leans out at the top, away from the vehicle, it is said to have a positive camber angle. With a negative camber angle, the wheel leans inward at the top. Zero camber is defined as having the wheel/tire perpendicular to the road surface. Changes in camber can occur when the vehicle body leans during a turn and when the wheels move vertically through jounce and rebound. A wheel set at a camber angle produces “camber thrust,” which is a lateral force generated in the direction of the lean. Camber angle can be utilized to maximize cornering forces by keeping the outside tire upright or at a slightly negative camber angle as the body leans to the outside of the turn. Camber can also be utilized to minimize lateral movement, or tire scrubbing, at the contact patch. Camber change can also compensate for body roll to keep the outside wheel from lean away from the turn. Tire scrubbing (changes in the tread) can be minimized by good suspension design, and camber changes should be minimal as well. Rear wheel camber changes can augment cornering forces, and they can influence the balance between oversteer and understeer.
When camber specifications are determined during the design stage, a number of factors are often taken into account. The engineers often account for the fact that wheel alignment specifications used by alignment technicians are for a vehicle that is not moving. On many vehicles, camber changes with different road speeds. This is because aerodynamic forces cause a change in riding height from the height of a vehicle at rest. Because of this, riding height is commonly checked and problems corrected before setting camber. Camber specs are set so that when a vehicle is at highway speed, the camber is at the optimal setting for minimum tire wear.
Despite the often significant effects of camber on vehicle performance, often adjustments in camber are not easily implemented after vehicle assembly. Modifications to vehicle design, alterations in performance over vehicle lifetime, replacement of automotive components with non-OEM parts all can play a factor in altering the benefit of a camber angle set during original vehicle design. It would, therefore, be highly desirable to have a control arm assembly that allowed for a simple and effective adjustment to camber. Such an assembly would provide both improved maintenance of automotive performance, but could be utilized to provide increased design flexibility as well.